Motor control.



PATENTED JUNE 18, 1907 P. BIOHBERGL MOTOR CONTROL. APPLIOATION FILED JAN.11. 1905.

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current to the rotor winding.

riunniucn nionnnno, or solemn,

GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATKO'N OF NEXV YORK.

MOTOR CONTROL.

I Specification of Letters I-stent.

PatentectJune 18. 1907.

Application filed January 11, 1905. Serial. No. $10,551.

To all whom, it ntcty concern:

Be it known that I, Finnniucu Eionnene, a subject of the Emperor of Austria, residing at Berlin, in the Empire ol Germany, have invented certain new and useful improvements in Motor Control, of which the follow ing is a specification.

My invention relates to the control of alternating current comn'iutator motors of a type disclosed ipa tormer application, Serial No. 146,692, iiltil by Gabriel Winter and myself March 7, 1903, and its object is to provide means whereby such motors may be op erated elliciently on either alternating or direct current.

The type of motorto which I refer, as disclosed in the above mentioned application, comprises a stator winding and a. rotor wind ing provided with a connnutator and two sets of brushes. One set oi brushes short.- circuits the rotor winding on the line of magnetization produced by the stator winding, while the other set is connected in series with the stator winding, either directly or through a transl'ormcr, and supplies the magnetizing The iield produced by this magnetizing current coacting with the currents in the stator winding and the rotor short-circuit produces the motor torque.

It is sometimes important that it should be possible to operate motors both on alternating and direct current as, for instance,in the case of an electrically-operated vehicle.

My invention consists in providing means for connecting 'a motor, which is connected for operation on alternating current as above described, so as to secure ellicient operation on direct current.

When operating on direct current the stator winding and the brushes, which in alternating current operation supply the magnetizing current, are connected directly in series with'the direct current source, and'the flow of current through the rotor short-circuit is prevented. The stator winding then acts as the field, and the rotor, with its brushes displaced 90 degrees from the field, as the armature of an ordinary direct current series motor. That the motor is particul'arly adapted for ellicient operation, with the'respective connections as set forth above, both on alternatin and direct cur rent, is evident from the following consideracarry tions: In an alternating current motor, in order that the power factor should be high, it is well understood in the art that the ma;

netising ampere turns should be small as compared with the ampere turns carrying energy current, while in a direct. curren t motor for etlicient operation it is essential that the hold ampere turns should be great as compared with the armature ampere turns.

When the motor is connected for alt ating current. operation, the stator w nding carries the energy current, while the armature brushes displaced 90 degrees thercl'rom the magnetizing current. (onsequently, for ellicient operation the stator ampere turns should be great as compared with the rotor ampere turns. Since in direct current operation the stator acts as the field and the rotor as the armature, the proportion of stator and rotor ainpcre turns adapted to give ollicient operation on alternating current is exactly the proportion desirable for direct current operation.

My invention n ill best be understood by reference to the accompanying drawings, in which Figure 1 shows diagrannnaticall amotor of the commutator type provided with acontrolling switch arranged in :wcordance with my invention for connecting the motor or operation on either alternating or direct current; Figs. :2 and 3 are diagrams oi .the connections obtained when the controlling switch of Fig. 1 is in its two' positions; Fig. 4 shows a modified arran ement oi the controlling switch; and Figs. 0 and 6 are diagrams showing the circuit connections obtained by the controlling switch of Fig. 4.

Referring first to Fig. 1, M represents the motor which comprises the stator winding S and the rotor winding it provided with two sets oi commutator brushes, one set, I; 1), arranged on the line of the. stator hold, and the second set, I) b, displaced 9t) electrical degrees therefron1. A represents a source of alternating current, and l) a source of direct current. C represents a controlling switch by means of which the motor is connected to either source.

When the controlling switch is moved to bring the'movable contacts on the dotted line a into engagement with the stationary contacts, a circuit is completed as follows: from the lower. lin e wiire A, Contact 0, contact 0 stator S, lower brush l2", upper brush 1), contact contact to upper line-wire A. The brushes 1) l) on the line of the stator field are electrically connected through the contacts 5, c and c'. The stator winding S and the brushes i) b are thus connected in series with the source, While the brushes b short-circuit the rotor on the line of the stator field.

This is the connection for alternating curio rent operation, as set forth in the former application referred to above. These connections are shown diagrammatically in Fig. 2. s... .lL-the controlling switch C is moved to bring the movable-contacts on the line cl into engagement with the stationary contacts, a

circuit is closed from lower linewire D, contact 6*, contact 0 stator winding S, through brushes b, contact 0 contact :2 to upper line-wire D. The brushes 1) b are open-circuited. This connection is shown in i 'ig. 3.

The motor is thus connected as an ordinary series motor and a fiow of current between the brushes 6 b, due to the electromotive force produced in the rotor winding by its 2 5 rotation in the field produced by the armature current, is prevented by breaking the electrical connection between these brushes.

As has been pointed out heretofore, it the rotor ampere turns are made small in proportion to the stator ampere turns, the connection shown in Fig. 2 will give erficient operation on alternating current, since the stator winding carries the energy currents,

while the rotor Winding between the brushes 3 5 b b carries the magnetizing currents. Also with the connection of Fig. 3, the hold umvpere turns will be strong compared to the armature ampere turns, and el'licient operation as a direct current motor is obtained.

It is sometimes desirable in operating a motor on alternating current to connect the brushes l) l) in series with the stator winding through a series transformer instead of directly, either to obtain a speed regulation 4 5 by varying the ratio of transformation of the transformer or to renderit ossible to operate the motor on a higher vo tage than could be impressed on the commutator. In such a case, the transformer must evidently be cut out of circuit when the motor is operated on direct current. Furthermore, in the case of lar e motors with the rotor wound for low vo tages, and consequcntlya high current capacity, it is sometimes inconvenient to lead the connections from the shortcircuiting brushes b b to the controllin; switch, particularly if the controlling switch is placed at some distance from the motor. In such a case is necessery to provide other means \thbreaking the short circuit for Preventing" t Brent-flow between these brushes when mo r operated on direct current. A i above modificaf bns are shown in the ngeinent of Fig. 4. hi t s series transforme T is provided for connecting the brushes 1; Z) in series with the stator winding S, and an auxiliary stator winding S is provided for inducing an electromotivelorce the rotor winding between the short-ch'cuiting brushes 6 Z), which is equal and opposite to that induced by the field produced by the armature current; or, in other words, the ampere turns of the auxiliary winding S neutralize the rotor ampere turns between the brushes 1) b. The circuits withthis arrangement are as follows: Nhen the controlling switch C is moved. to bring the movable contacts on-the line a into engagement with the stationary contacts, a circuit'is closed from upper linewire A, contact 0 contact 0, through stator winding S; through the primary of transfOTDlGP' il, contact 0, contact to lower linewire A. A. circuit is also completed from the upper terminel oi the secondary of transformer T to upper brush 1), lower brush 6, contact 0, contact c, to the lower terminal of the transformer secondary. The brushes 6 l) are thus placed in series with the statol winding S through the transformer T. The brushes 6 l) are permanently short-clrcuited inde mndently of the controlling switch.

'Vlhen the controlling switch (3 is moved to its other position, the following circuits are completed: from upper line-wire D, contact contact c",-sta-tor winding S, contact 0 contact c lower brush 1), upper brush 1), auxiliary stator winding 8, contact 0 contact 0 to lower line-wire l The stator winding 8, the rotor brushes b l) and the auxiliary or compensating winding S are all connected directly in series to the source and the transformer T is out out of circuit. Since the compensating field S" is in series with the rotor, it will, if properly proportioned, neutralize the field produced by the rotor current for all loads on the motor. Consequently no electromotive force can be induced between the brushes 5 b by the rotation of the motor, and the flow of current between these brushes, when the motor is operatin on direct current, is prevented as cillectual y as if the electrical connection between these brushes were broken.

While for the sake of simplicity I have shown the motor diagrammatically,it will be understood that any well known form of construction may be employed. The stator winding is preferably a distributed winding disposed in slots on a laminated core, while the rotor is provided with a winding on the commutator similar to that of a. direct current machine. The arrangement of the com may be moved as desired. r'lccordiugly, I do not desire to limit myself to the particular construction and arrangement here shown, but aim in the appended claims to cover all modifications which are within the scope of 8 my invention.

trolling switch, its contacts and connections Furthermore it is obvious that for the purhoses of my invention it makes no difference in operation on alternating current whether the rotor brushes are connected in series with the" stator conductively or inductively through a transformer, and consequently when I employ the term in series in the appended claims, I desire it to'be understood that I include both a direct series connection and an indirect series connection through a transformer.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1 In combination with an alternating current motor of the commutator type having two sets of commutator brushes, one on the line of the stator field and the second displaced 90 electrical degrees therefrom, means to r connecting the stator winding and second set of brushes in series to an alternating current source and short-circuiting the first set of brushes, and means for connecting said stator winding and second set of brushes in series to a direct current source andpreventing a flow of current. between the brushes of the first set. I

2. In combination with an alternating cur rent motor of the commutator type having two sets of commutator brushes, one on the line of the stator field and the second displaced. 90 electrical degrees therefrom, means for connecting the stator Winding and secondset of brushes in series throughatransformer to an alternating current source and shortcircuiting the second set of brushes, and means for connecting said stator winding and second set of brushes directly in series to a direct current source and preventing a fiow of current between the brushes of the first set.

3. In combination with an alternating current motor of the commutator type having two sets of commutator brushes, one on the line of the stator field and the second displaced 90 electrical degrees therefrom, transformer, means for connecting the stator winding of the motor and the primary of said transformer to an alternating current source, connecting the second set of brushes to the secondary of said transformer, and shortcircuiting the first set of brushes, and means for connecting the stator winding and said second set of brushes in series to a direct current source, cutting said transformer out of circuit, and preventing a flow of current between the brushes of the first set.

In witness whereof, I have hereunto set my hand this twenty-first day of December, 1904.

FRIEDRICH nicrnsnns.

Witnesses:

HENRY I-IAsPEn,

WoLnEMAn HAUPT. 

